The main objective of this research is to study the mechanism of food vacuole formation (phagocytosis) in Tetrahymena, its contribution of the general physiology of the cell, and its dependence on other vital cellular functions. To accomplish this we intend to perform a genetic dissection, that is, to obtain a collection of mutants which are individually defective in single, different components of this interesting mechanism, characterize the defect to each mutant down to the molecular level if possible, and thereby characterize the normal mechanism in the wild-type strain. We have demonstrated the feasibility of this approach by isolating a mutant which is temperature-sensitive for food vacuole formation. A second objective is to study the mechanism of adaptation to cycloheximide, by exploiting the dramatic changes in the rate of food vacuole formation caused by this inhibition of protein syntheis. We expect this study to be significant in that (a) it will introduce a novel and incisive experimental tool in the study of phagocytosis; (b) these mutants will provide a means of clarifying the relative importance of the routes of entry of nutrients and drugs into the Tetrahymena cell and to determine the relationship of food vacuole formation to other important cellular processes, such as membrane cycling, lysosome formation, synthesis and routes of excretion of hydrolytic enzymes; (c) greater understanding of the rate of food vacuole formation as a "vital sign" may furnish a new tool for genetic dissection of other "life support systems"; (e) finally, concepts and approaches developed in this study may find application in basic and clinical medicine, in view of the important roles played by phagocytosis in the immune response and in the clearing of particulate matter. This study may yield a better understanding of blood diseases and lung diseases traced to disorders of phagocytosis and to microparticle pollution.